1. Field of the Invention
The present invention relates to a booster type high-pressure vessel that is available for cold hydrostatic pressurizing treatment or the like.
2. Description of the Prior Art
The inventors of this invention developed and previously proposed a self-balancing booster type high-pressure vessel provided with a booster piston as a super high-pressure container having a high factor of safety that is available for cold hydrostatic pressurizing treatment or the like.
The above-referred known as a self-balancing booster type high-pressure container has a basic construction as shown in FIG. 4. More particularly, with reference to FIG. 4, a high-pressure vessel (1) comprises an outer cylinder (1a) having an upper lid (2) and a lower lid (3) fitted thereto, and an inner cylinder (1b) fitted inside the outer cylinder (1a) with a gap clearance (.alpha.) retained therebetween, and packings (5) around the inner cylinder (1b), the upper lid (2) and the lower lid (3). In addition, a piston (4) having a stepped configuration is fitted between the upper lid (2) and the upper portion of the inner cylinder (1b) in a vertically slidable manner, a larger diameter portion and a smaller diameter portion of the piston (4) being disposed within the outer cylinder (1a) and the inner cylinder (1b), respectively, in a liquid-tight and slidable manner by packages (5). A high-pressure liquid medium (P.sub.1) is poured and fed onto a top surface (4a) of the piston (4) through feed pipes (a.sub.1) and (a.sub.2) and a feed hole (6) provided in the upper lid (2). In the piston (4) is an inflow hole (10) associated with a spring-loaded check valve (10a), which hole is disposed so as to communicate with the feed hole (6) and the interior of the inner cylinder (1b). Also, an escape hole (8) is provided in the outer cylinder (1a) so as to communicate with a space (7) confined between the piston (4) and the top portion of the inner cylinder (1b). This escape hole (8) is connected with a feed pipe (a.sub.3) and an exhaust pipe (b.sub.3) of a low-pressure liquid medium (P.sub.4), and another exhaust pipe (b.sub.5) is connected with an exhaust hole (9) provided in the lower lid (3).
In addition, in FIG. 4, reference character (A) designates a pressure setter, reference characters (B), (C) and (D) designate high-pressure gate valves provided in the exhaust pipes (b.sub.5), (b.sub.3) and (b.sub.1), respectively, reference numeral (E) designates a check valve provided in the feed pipe (a.sub.3) and reference character (F) designates a pressure gauge disposed in the exhaust pipes (b.sub.1) and (b.sub.3).
Since the booster type high-pressure vessel shown in FIG. 4 is constructed as described above, if the interior of the inner cylinder (1.sub.b) is filled with a liquid medium to bring it into the state shown in FIG. 4 and a high pressure P.sub.1 is applied to the top surface (4a) of the piston (4) by injecting a high-pressure liquid medium (P.sub.1) through the feed hole (6), then the piston (4) moves downwards, hence the liquid medium within the inner cylinder (1b) is boosted up to a pressure P.sub.2, and then balance of the loads applied to the piston (4) is represented by the following equation: EQU P.sub.1 A.sub.1 =P.sub.2 A.sub.2 +P.sub.3 A.sub.3 ( 1)
where
A.sub.1 : pressure receiving area of the top surface of the piston (4) PA1 A.sub.2 : pressure receiving area of the bottom surface of the piston (4) PA1 A.sub.3 : pressure receiving area of the stepped portion of the piston (4) EQU A.sub.1 =A.sub.2 +A.sub.3 ( 2)
The balancing condition is represented by Equations ( 1) and (2) above, and the relation of P.sub.2 &gt;P.sub.1 &gt;P.sub.3 is fulfilled, that is, compared to the pressure P.sub.1 of the high-pressure liquid medium (P), the boosting liquid medium pressure P.sub.2 of the liquid medium within the inner cylinder (1b) is high, while a pressure P.sub.3 within the space (7) and the gap clearance (.alpha.) is low.
In the above-described known booster type high-pressure vessel, the inner cylinder (1b) forming the high-pressure vessel is designed so as to have a rating pressure adapted for the pressure (P.sub.2 -P.sub.3), while the outer cylinder (1a) is designed so as to be adapted for the pressure P.sub.1, hence the entire high-pressure vessel is designed so as to be adapted for the pressure (P.sub.1 +P.sub.2 -P.sub.3), and so, the vessel is constructed so as to have a large wall thickness. Further, in accordance with the design of the container, the force applied to a yoke frame (not shown) for supporting the high-pressure vessel also becomes large. Hence, a large-sized yoke frame becomes necessary, and since the inner cylinder (1b) is subjected to a pressure variation of the pressure (P.sub.2 -P.sub.3), the fatigue strength of the inner cylinder cannot be sufficiently assured. Moreover, upon loading of a work to be treated, it is necessary to mount and dismount the upper lid to and from the piston, and so, troublesome operations are necessary. The known booster type high-pressure container was associated with such technical problems to be resolved.